1. Field of the Invention
The present invention relates to a method for manufacturing a magnetoresistive effect (MR) element, to a method for manufacturing a thin-film magnetic head with an MR element, and to a thin-film magnetic head with an MR element.
2. Description of the Related Art
As hard disk drive apparatuses (HDD) increase in capacity and reduce in size, highly sensitive and high-output thin-film magnetic heads are being demanded. In order to satisfy the demand, performance of giant magnetoresistive effect (GMR) thin-film magnetic heads with GMR read head elements are being improved. On the other hand, tunnel magnetoresistive effect (TMR) thin-film magnetic heads with TMR read head elements having a magnetoresistivity ratio more than twice as high as that of the GMR thin-film magnetic heads are being developed.
TMR thin-film heads differ from conventional GMR thin-film magnetic head in head structure because of the difference in the flowing direction of sense current. The head structure in which sense current flows in a direction parallel to the layer planes or film planes as in typical GMR thin-film heads is called as CIP (Current In Plane) structure, whereas the structure in which sense current flows in a direction perpendicular to the film planes as in TMR thin-film magnetic heads is called as CPP (Current Perpendicular to Plane) structure, respectively.
In fabrication of a GMR thin-film magnetic head with the CPP structure or a TMR thin-film magnetic head, it is important to ensure the flatness of a lower shield layer or lower electrode layer and an upper shield layer or upper electrode layer in order to improve the stability of the MR element.
If the upper shield layer is not flat but has asperities, coupling between this upper shield layer and a magnetization free layer or a free layer in the MR multi-layered structure may induce unstable operations of the MR element. Also, such asperities in the upper shield layer will induce lowering of the resolution of the MR element causing difficulty for high recording density.
The applicants of this application have proposed a method for manufacturing a thin-film magnetic head, having a step of depositing an MR multi-layer, a step of patterning the deposited MR multi-layer by milling with a mask to form an MR multi-layered structure, a step of depositing an insulation layer on a cap layer and a lower electrode layer at the top of the formed MR multi-layered structure, a step of planarizing the deposited insulation layer until the cap layer of the MR multi-layered structure is exposed, and a step of forming an upper electrode layer on the planarized insulation layer and MR multi-layered structure (U.S. Pat. No. 6,669,983 B2).
The manufacturing method described in U.S. Pat. No. 6,669,983 B2 is advantageous in that the upper electrode layer can be planarized. However, it is required to perform a planarization process such as chemical-mechanical polishing (CMP) and it is necessary to form the cap layer considerably thick at the top of the MR multi-layered structure.